On the level describes someone’s honest work ethics. The prophet Amos spoke about a plumb-line, which measures vertical as opposed to horizontal straightness.

He’s a law unto himself means he makes up his own rules and his behaviour cannot be predicted. St Paul wrote this in connection with the Gentiles, who did not have the Law of Moses. Romans 2:14 It echoes words from the Book of Judges, which describes a period in the history of Israel when everyone did what they saw fit. Judges 21:25